linux-kernel - Re: [PATCH v3 2/5] PCI: imx6: Don't poll LTSSM state of i.MX6QP PCIe in PM operations

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Message-ID: <aFQih1GVoWwC9WEb@lizhi-Precision-Tower-5810>
Date: Thu, 19 Jun 2025 10:45:27 -0400
From: Frank Li <Frank.li@....com>
To: Richard Zhu <hongxing.zhu@....com>
Cc: jingoohan1@...il.com, l.stach@...gutronix.de, lpieralisi@...nel.org,
	kwilczynski@...nel.org, mani@...nel.org, robh@...nel.org,
	bhelgaas@...gle.com, shawnguo@...nel.org, s.hauer@...gutronix.de,
	kernel@...gutronix.de, festevam@...il.com,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/5] PCI: imx6: Don't poll LTSSM state of i.MX6QP PCIe
 in PM operations

On Thu, Jun 19, 2025 at 05:12:11PM +0800, Richard Zhu wrote:
> Refer to PCIe r6.0, sec 5.2, fig 5-1 Link Power Management State Flow
> Diagram. Both L0 and L2/L3 Ready can be transferred to LDn directly.
>
> It's harmless to let dw_pcie_suspend_noirq() proceed suspend after the
> PME_Turn_Off is sent out, whatever the LTSSM state is in L2 or L3 after
> a recommended 10ms max wait refer to PCIe r6.0, sec 5.3.3.2.1 PME
> Synchronization.
>
> The LTSSM states of i.MX6QP PCIe is inaccessible after the PME_Turn_Off
> is kicked off. To handle this case, don't poll L2 state and add one max
> 10ms delay if QUIRK_NOL2POLL_IN_PM flag is existing in suspend.
>
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>

Reviewed-by: Frank Li <Frank.Li@....com>

> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 5a38cfaf989b..8b7daaf36fef 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -125,6 +125,7 @@ struct imx_pcie_drvdata {
>  	enum imx_pcie_variants variant;
>  	enum dw_pcie_device_mode mode;
>  	u32 flags;
> +	u32 quirk;
>  	int dbi_length;
>  	const char *gpr;
>  	const u32 ltssm_off;
> @@ -1759,6 +1760,7 @@ static int imx_pcie_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>
> +	pci->quirk_flag = imx_pcie->drvdata->quirk;
>  	pci->use_parent_dt_ranges = true;
>  	if (imx_pcie->drvdata->mode == DW_PCIE_EP_TYPE) {
>  		ret = imx_add_pcie_ep(imx_pcie, pdev);
> @@ -1837,6 +1839,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.enable_ref_clk = imx6q_pcie_enable_ref_clk,
>  		.core_reset = imx6qp_pcie_core_reset,
>  		.ops = &imx_pcie_host_ops,
> +		.quirk = QUIRK_NOL2POLL_IN_PM,
>  	},
>  	[IMX7D] = {
>  		.variant = IMX7D,
> --
> 2.37.1
>